agraquest-logo.jpgDavis, Calif.-based AgraQuest, an ag-biotech firm developing new forms of pesticide, raised $20 million in what appears to be its tenth major fundraising. The U.K.’s Loudwater Trust and existing investors, including TPG Ventures, participated in the round.

AgraQuest derives novel, organic pesticides from natural microorganisms, which the company screens in order to identify natually produced substances that have toxic effects on pests. The full process, which AgraQuest details on its Web site here, is actually quite interesting. Essentially, the company IDs a bug that seems to have evolved a decent pest-control defense, analyzes that substance to ensure that it’s not toxic to plants or other animals, and then mass-produces it using biotech methods, basically by fermenting batches of the microorganisms in big vats and then purifying the resulting pesticide.

Founded in 1995 and with a half-dozen products on the market, AgraQuest is getting a bit long in the tooth for a venture company. It tried to go public a few years ago, but withdrew its filing in 2002. It has since raised more than $60 million including the latest funding, which the company is billing as a “mezzanine” round, according to VentureWire. AgraQuest has also survived the loss of a founder, Pam Marrone, who left last year to found a competing firm, Marrone Organic Innovations.